1. Field of the Invention
This invention relates to an information retrieval device, and more particularly to a device for selecting and bringing to a projection station a transparency from among a number of transparencies which carry fixed information and are stored in a vertically stacked form.
2. Description of the Prior Art
It has been known in the art to display a computer output on a cathode ray tube and record the displayed output on a microfilm. The device used for this purpose is called Computer Output Microfilmer, which will hereinbelow be referred to as COM. The COM is practically very convenient since the recorded output can be long stored, easily duplicated, easily distributed and easily retrieved. For making the record of information in good form, the output information displayed on the cathode ray tube is combined with an image of fixed information such as items, lines of a frame of a table etc. The fixed information is recorded in advance on a transparency and the image of the transparency is optically combined with the displayed output information by use of a semi-transparent mirror or the like. The combined information is photographed by a microcamera. The transparency is usually in the form of a lithographic plate fixed to a metal mount. This transparency will hereinbelow be referred to simply as "format film".
In the conventional COM, it has been known to use a rotatable turret on which a number of format films are mounted and selectively brought to a projection station. The turret type format film holder is disadvantageous in that the format films are radially arranged and accordingly occupy a large space and need fine position adjustment of the turret for precisely bringing the format film to the predetermined projection position.